scholarly journals Implementation of an unloading compliance procedure for measurement of crack growth in pipeline steel

2011 ◽  
Vol 2 (3) ◽  
pp. 397-406
Author(s):  
Koen Van Minnebruggen ◽  
Dries Van Puyvelde ◽  
Wim De Waele ◽  
Matthias Verstraete ◽  
Stijn Hertelé ◽  
...  
Keyword(s):  
Crack Growth ◽  
Fossil Fuels ◽  
Standardized Test ◽  
Pipeline Steel ◽  
Test Procedure ◽  
Ductile Failure ◽  
Single Edge ◽  
Single Edge Notch ◽  
Edge Notch ◽  
Unloading Compliance

As the demand for fossil fuels increases, pipelines are constructed in inhospitable areas. Underthese conditions, not only the strength but also the deformability of the pipelines becomes crucial. A strainbased design (SBD) procedure needs to be established. Traditional stress based approaches to evaluatedefect tolerance lead to conservative predictions. There is a need to accurately define the fracturetoughness of the pipeline steel and assess the criticality of weld defects under strain based conditions. Thispaper focuses on the implementation of the unloading compliance method to determine stable crackgrowth. The standardized test procedure described in ASTM E1820 is applied. This method is a handy toolto obtain the J-resistance curves which can forecast ductile failure in pipeline girth welds. Preliminaryexperiments have been performed on Single Edge Notch Bend (SENB) specimens of plain pipe metal.Using the implemented procedure, it was possible to obtain a good fit between calculated and measuredcrack size. The most important result is the smoothness of the calculated crack growth and the rathermonotonic increase of crack size. Since testing on SENB is well known to provide conservativemeasurements, Single Edge Notch Tension (SENT) specimens will be evaluated in future work

scholarly journals Modelling the Variability and the Anisotropic Behaviour of Crack Growth in SLM Ti-6Al-4V

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1400
Author(s):  
Rhys Jones ◽  
Calvin Rans ◽  
Athanasios P. Iliopoulos ◽  
John G. Michopoulos ◽  
Nam Phan ◽  
...  
Keyword(s):  
Crack Growth ◽  
The United States ◽  
Fatigue Threshold ◽  
Growth Equation ◽  
Single Edge ◽  
Test Program ◽  
Large Variability ◽  
Single Edge Notch ◽  
Anisotropic Behaviour ◽  
Edge Notch

The United States Air Force (USAF) Guidelines for the Durability and Damage Tolerance (DADT) certification of Additive Manufactured (AM) parts states that the most difficult challenge for the certification of an AM part is to establish an accurate prediction of its DADT. How to address this challenge is the focus of the present paper. To this end this paper examines the variability in crack growth in tests on additively manufactured (AM) Ti-6Al-4V specimens built using selective layer melting (SLM). One series of tests analysed involves thirty single edge notch tension specimens with five build orientations and two different post heat treatments. The other test program analysed involved ASTM standard single edge notch specimens with three different build directions. The results of this study highlight the ability of the Hartman–Schijve crack growth equation to capture the variability and the anisotropic behaviour of crack growth in SLM Ti-6Al-4V. It is thus shown that, despite the large variability in crack growth, the intrinsic crack growth equation remains unchanged and that the variability and the anisotropic nature of crack growth in this test program is captured by allowing for changes in both the fatigue threshold and the cyclic fracture toughness.

Comparison of Fatigue Crack Growth Rates Between Different Specimen Geometries

2021 ◽  
Author(s):  
Yan-Hui Zhang ◽  
Matthew Doré
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Literature Review ◽  
Crack Growth ◽  
Compact Tension ◽  
Specimen Geometry ◽  
Single Edge ◽  
Single Edge Notch ◽  
Advantages And Disadvantages ◽  
Edge Notch

Abstract Most engineering components are subjected to cyclic loading in service and design against fatigue failure is often a key consideration in design. For fracture mechanics fatigue analysis, fatigue crack growth (FCG) tests are often required to determine the relevant Paris power law parameters for the material under the environment concerned. Standards allow use of different specimen geometries for FCG tests such as compact tension (CT), centre crack tension (CCT), single edge notch bend (SENB) and single edge notch tension (SENT). However, when selecting specimen geometry for fatigue crack growth rate (FCGR) testing, there is often doubt about which specimen geometry is more appropriate and whether they give similar FCGR. There is limited work to compare the FCGR between different specimen geometries. This paper first briefly introduces the guidance on FCG test specimen geometries in standards and compares the advantages and disadvantages of these specimen geometries. A comprehensive literature review is carried out to compare the FCGR data between different specimen geometries. FCGR tests are conducted on SENB, SENT and CCT specimens of C-Mn steel to investigate any effects of specimen symmetry/asymmetry and crack constraint on FCGR. Based on the literature review and test data, it is concluded that FCGR is independent of the specimen geometries examined.

A single edge notch specimen for fatigue, creep-fatigue and thermo-mechanical fatigue crack growth testing

2018 ◽  
Vol 199 ◽  
pp. 760-772 ◽  
Author(s):  
Santosh B. Narasimhachary ◽  
Kanwardeep S. Bhachu ◽  
Sachin R. Shinde ◽  
Phillip W. Gravett ◽  
James C. Newman
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Single Edge ◽  
Single Edge Notch ◽  
Mechanical Fatigue ◽  
Creep Fatigue ◽  
Edge Notch ◽  
Fatigue Crack Growth Testing

The use of the C∗ parameter in predicting creep crack propagation rates

1977 ◽  
Vol 12 (3) ◽  
pp. 167-179 ◽  
Author(s):  
M P Harper ◽  
E G Ellison
Keyword(s):  
Crack Propagation ◽  
Crack Growth ◽  
Creep Crack Growth ◽  
Compact Tension ◽  
Single Edge ◽  
Single Edge Notch ◽  
Creep Crack ◽  
Edge Notch ◽  
Single Edge Notch Bend ◽  
Good Agreement

The applicability of the C∗ parameter for the prediction of creep crack propagation rates is considered. A new method for estimating C∗ is presented, the results from which show good agreement with those from an existing technique. Experimental results from creep crack growth tests, conducted on a 1 Cr Mo V steel using both compact tension and single edge notch bend specimens, indicate that good correlation with C∗ is obtained once the effects of stress redistribution become negligible. Finally, comparisons are drawn between C∗ and other possible correlating parameters, and the limitations of each approach are discussed.

Acoustic Emission Monitoring During Fatigue Crack Growth in Standard C(T) and Miniature Single Edge Notch Tension Specimens

2020 ◽  
Author(s):  
Raghu V. Prakash ◽  
Chandan K. Mukhopadhyay ◽  
Prathmesh Pokharkar ◽  
Manuel Thomas
Keyword(s):  
Growth Rate ◽  
Acoustic Emission ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Compact Tension ◽  
Single Edge ◽  
Single Edge Notch ◽  
Edge Notch

Abstract The fatigue crack growth rate studies in a structural alloy has been carried out using ASTM E-647 standard compact tension (C(T)) specimens and miniature single edge notch tension specimens (SEN(T)) at two different stress ratios of 0.1 and 0.7. Standard C(T) specimen had a dimension of 63.5 × 61 × 8 mm thickness while the miniature SEN(T) specimen had a size of 20 mm effective length × 10 mm wide and 0.7 mm thickness. A starter notch of 0.5 mm was cut using wire EDM process to initiate fatigue crack growth in miniature SEN(T) specimen. A special fixture was designed for testing the miniature SEN(T) specimen. During the fatigue crack growth experiments, Acoustic Emission (AE) activity was monitored on-line using AE sensors from Physical Acoustics, Mistras Group, USA. For the experiments on standard C(T) specimens, a standard probe (R15A) of 15 mm diameter was used, while for small size compact tension specimen, a Nano30 AE probe was used. The crack growth was monitored by visual methods as well as by compliance technique. The cumulative counts and absolute energy information obtained during fatigue crack growth testing was used to correlate the crack growth rate with acoustic emission activity. Empirical fit of data was used to obtain cross-correlation between crack growth rate and AE parameters for both the specimen geometries. The study suggested that suitable selection and placement of sensors is essential to obtain good results using AE sensor technique.

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